MSD Animal Health is reassuring producers who are using Bovilis BVD vaccine that it will not confuse the results of standard BVD PCR ‘tag and test’ testing. An inactivated BVD strain is used in the vaccine, which cannot be transferred from the dam to the foetus.
“When it comes to BVD control, at a practical farm level we strongly recommend two crucial steps,” says the company’s vet adviser Andrew Montgomery. The first is to find the persistently infected (PI) calves and remove them. And the second is to prevent any more PI calves being born.
Testing ear-notch samples
“Producers can find new-born PI calves by testing ear-notch samples. If a live BVD vaccine is used, then the vaccine strain may be passed to the foetus, giving a positive result to standard ‘tag and test’ PCR screening.
“As with any positive test, producers must wait three to four weeks during retesting to see if the virus clears and possibly undertake more detailed virus screening. And this can cause confusion and anxiety. Further testing establishes whether the results are from the vaccine strain or a new case of the field strain.
He adds that to help prevent any more PI calves being born, heifers should be vaccinated. “This is important in curbing the spread of BVD, as avoiding PIs being born is key to breaking the cycle of disease. Bovilis BVD boosters can be used safely at any time during pregnancy, providing foetal protection.
“The primary course consists of two vaccinations, which are given four weeks apart to cattle above the age of eight months, to be completed four weeks before pregnancy. The first booster is given six months later and then at 12-month intervals,” he adds.